Rubber and process of treating same



Patented July 7, 1936 UNITED STATES wisest PATENT ol -Firs RUBBER AND PROCESS OF TREATING SAME Frederick J. Maywald, Rutherford, and Eric C. Kunz, Montclair, N. J.

No Drawing. Application July 19, 1932, Serial No. 623,392

6 Claims.

the manufacture of perfume, which when com-' bined with a rubber compound and cured, or combined with cured rubber, either mask the objectionable odor found in many rubber products or not only mask the objectionable odor but impart a permanent pleasing odor thereto. In said application it is further disclosed that in the presence of an accelerator, specifically diphenylguanidine (D. "P. Gi) the odorizing or 'deodorizing proceeds much more quickly and smaller quantities of the deodorizing principle are required, and also that where it is simply desired to mask the normal objectionable odor, less odorizing principle is required than where it is desired to impart a definite scent to the finished rubber.

In continuation-of our researches, in combining what we willbr-oadly call odorants with rubber, we have now found that certain classes of odorants when combined with rubber not only odorize the finished rubber products, but in addition thereto usefully and unexpectedly act as retardants .of scorching with other accelerators, or plasticizers, or accelerators, or anti-oxidants or anti-suncracking agents or in some instances combining these functions, or two of them, and thereby producing an entirely new species of rubber prodnot of increased durability and pleasing odor as compared with similar products now on the mar- 'ket. In some instances our materials give the finished goods marked germicidal qualities. Heretofore in curingrubber, organic accelerators used contained nitrogen or sulphur or both. The materials of this invention do not contain nitrogen or sulphur. Without intending to restrict ourselves to the goods named, ourinvention is-of marked utility in air or heat cured rubber goods for personal and household use, "toys, sheeting, ice and hot water bags, tubing, rubber coated fabric, gum and'latex rubber products, and various more'or less highly compounded stocks, made in whole or in part of latex, gum rubber, reclaim, batata, guayule, synthetic rubber mixtures, etc. Rubber goods cured by the air or dipping process, in which the dipping solution contains the perfume materials, have increased strength, and are especially suitable for many purposes, as for example, balloons, protective and sanitary devices, etc. Products made according to this invention have .a better sales appeal, and by using various odorizing materials the source of manufacture can be identified. It is known in the rubber art that certain accelerators highly useful in shortening the cure and increasing the tensile strength, impart a Very objectionable odor to the finished goods and hence are unsuitable for many goods, but we have found that by the use of our perfume inaterials such accelerators can now be used and scorching reduced, or the curing curve flattened and prolonged. Goods so treated either have a neutral odor or a desired pleasing scent, and the goods in addition resist oxidation and suncracking for a longer period, and have both a higher initial tensile strength and a high strength after aging inan oven, equivalent to five or ten years ordinary exposure. y

Heretofore, no method of satisfactorily disinfecting rubber was known, as the use of the common antiseptics in rubber produced blooming and was otherwise harmful to the produce. We have also found that by the use of our perfume mate rials, the bacteria in rubber are killed, and that upon aging, the rubber remains free frombacteria and does not pick up bacteria in use. This is of great importance in children's rubber toys, and especially so of toys of such a nature or form that a child may place the twin his mouth, and circulate the toy among other children.

In carrying out our experiments we have cured control stocks with accelerators and then have cured the same stocks with various of our materials, and in all cases have not only de-odorized or odorized the product but have'accelerated its cure or increased the tensile strength, or have improved compounding and curing conditions, or have increased the aging, or resistance to suncracking, or improved the rubber in twoor'more of these respects. V

As both accelerators and rubber compounds vary so widely, and as the materials we have found useful are so numerous, it isx-impossible to test out each of such materials with each known rubber compound with and without eachknown accelerator, because the number of experiments,

required and the difierent effects from different kinds of cures and different temperatures would run into the millions, so in the further specific description of our invention and its manner of application required in a patent specification, we

can only give the general results of the several thousand tests conducted. The selected tests of particular accelerators and of particular stocks hereinafter described are illustrative, and not exelusive or limiting. In each case with the'matesistance.

V strength with and'withoutour materials may be r 1 unchanged, and. in some instances it is slightly in all cases with materially in creased aging, in oven tests equaling five and ten years exposure,

lower and in still. others increased slightly, but

in 1 Y r Another essential in the manufacture of rubber compounds where high-power or .ultra-accel and materially increasedresistance to suncrackerators are used is that during milling the com pound must not scorch orprecure, and some of our materials have been found to have the function of retarding such scorching in addition to the functions above mentioned. ;Also, in the manufacture of colored rubber goods it is important not to'use compounding or curing ingradients which discolor the rubber,;as by WP- pering, or whichdegrade the colors'usedin rubber, and our materials satisfy these requirements without causing porosityor other difficulties.

Odoriferous principles or products used for the manufacture of perfume aregenerally classed ac:-

cording to their principal ingredient, it being well knownin the perfume industry that secretmixture s under trade names may have as many as fifteen or more ingredients, some, of which ftradenamed compounds we have-successfully tested, but insofar as principal ingredients go, the ma 'terials suitable for our purpose, whetherstraight than .05 and less or mixed, can be classed about as follows:

Alcohols such asbenzyl alcohol, phenyl ethyl alcohol, phenyl propylal'cohol, cinnamic alcohol,

,anisic alcohol, methyl phenyl' carbinol.

Alcohols such as geraniol, citronellol, linalool. We do notattempt to enumerate in the foregoing all odoriferous products'usedin compounding a desired odor known to those familiar with the art but restrict our consideration to odoriferous alcohols having a phenol coefficient of more walker test. x r

All the above products or a mixture of two or more of these substances will odorize or deodorize rubber goods and improve the process as well as product in one or more ways.

The standard stock used was composedof:

. 7 "Parts Pale crepe rubber 500 'Whiting 125 Zinc oxide; 25 Magnesium oxide 5 1Sulp'hur;

and cures were madeiat fiftypounds steam (298 F.) for ninety minutes. This stock when freshly cured had a tensile'strength of 1620 pounds per'square inch withfelongation of 8.8;

A'sir'nilar stock was prepared using five parts 7 of D. P. G. 'inplace of the magnesiumoxide, and

for 20 minutes.

only 17.5 parts of sulphur, and cured at pounds Immediately after curing, the

stock had a tensile strength of. 2965 pounds per square inch and a'n'elong ation of 8.6.- After similar aging 100 hours. in" the oven, the tensile strength was 1272 pounds per square inch and the elongation 7.8. After similar aging 200 hours in the oven the tensile strength had dropped to fited thereby. V Hydrogenated cocoanut oil, which-is mainly an than V 19.5 modified Rideal- 2,046,336 H a a 585 pounds per square inch and-the elongation I H In general, similar quantities of the perfume materials are used, and from about 0.2% to 3% or more of such materials on the rubber'gives desired improvement'in quality,'subject t0 particular' product'sought', and can easily be deter- .mined by the compounder.

other accelerators with which our improvements give improved results comprise tetral methyl-thiuram' mono and poly sulphides, the salts of'dithio-carbamic acid such as the zinc salt of dimethyl-dithio-carbamic acid, theoxidizedzinc (salt of dimeth y-dithio carbamic. acid,

the lead salt of the same acid, piperidine-methyl dithio-carbamate salts, mercapto-benzoethiazole,

phenyl-alpha-naphthylamine, phenyl-beta-naph 1 thylamine, zinc-butyl xanthate, dibenzylamine,

diortho -tolyl-guanidine, aldehyde amine conden- I sation, products, xanthatesand derivatives, condensation products of di-methyl-para-phenylenediamine, thiuram-tetra-sulfid, guanidine esters."

hydrocarbon 'substitutediguanidinea; amino -alde-' hyde types, benzal-bis -di-methyl-di-thio-car bamate, some of which are both accelerators and} antieoxidants, with some known'anti-oxidants a a frequently used, which latter arefunnecessary With'this invention but the productsare benealcohol of the 'Cutype, has also worked Satisfactorily as an accelerator. 1 s

Other experiments employing benzyl alcohol, phenyl' ethyl alcohol, phenyl .propyl alcohol, have also shown favorable results in accelerating, aging and other qualities in various stocksvwitli and without softeners and other compounding materials, and with various accelerators.

every case mentioned herein .the products given either distinctly odorize thelrubber com. pound or give it a'neutralodorr Either odor can be gotten dependingson the amount of-perfunie' orjde-odorizing materlalused. r

An examination of the results of odoreven after a ten yearlife test, where one would expect the perfume product would be driven out of the rubber compound, we' find that this-is not the fact. 5

on thecontrary'we flnd that the odorof the rubber has beendistinctly covered, or hidden on neutralized. 'Most of theproducts would-indicate apparent combinations of sojme'or all of. the products-contained in' the perfuming material with th'erubber molecule. I Thesame results are obtained in the unaccelerate'cl stocks, as are'obe."

tion is present to a greater extent .on'the basis 'of the same amount of perfume material." When 7 we say fperfumematerial we refer toodorizing material, orde-odorizing material. I a Except where stated,-the cures havebeen'made V at the same time and temperature, but not neoessarily optimum cures ineach instance as that r is unnecessary in orderto determine the utility of this invention,'be,cause comparisons involving under-cures or over-cures with the standard stockwhich is approximately at optimum ,cure

can be made equally well; Therefore, we do not; .mean to be understood asstating that the'cures "7 above given using our materials are optimum cures and some are apparently under-cures;

- Summarizing the foregoing, the products hay-iing marked'anti-oxidant properties are linalool,

"tained in the accelerated stocks, except that in 5 some cases in the accelerated stock theodorizacures, because someof them areapparently overgeraniol, phenyl ethyl and phenyl propyl alcohol.

Those materials which have no substantial weakening effect on the product as first cured are geraniol, citronellol, linalool, phenyl ethyl and phenyl propyl alcohol.

Other materials may slightly reduce the tensile strength below that of the standard, but show up to better advantage in the samples after aging. Thus in the five year aging periods we find that the materials which have shown better results are geraniol, linalool, phenyl ethyl and phenyl propyl alcohol and citronellol.

Those in the ten year period are linalool and phenyl ethyl and phenyl propyl alcohol.

Among the products having anti-scorch properties is linalool.

We claim as our invention:

1. Process of treating rubber comprising adding thereto an organic accelerator and a substance selected from the group consisting of aroma-producing alcohols and esters thereof in an amount not exceeding 1.0% on the rubber, and vulcanizing the resulting mixture.

2. Process of treating rubber comprising adding thereto an organic accelerator and an amount of an aroma-producing substance selected from the group consisting of phenyl ethyl alcohol, phenyl propyl alcohol, cinnamic alcohol, anisic alcohol, methyl phenyl carbinol, geraniol, citronellol, linalool, terpineol, borneol and the esters ing the resulting mixture.

4. Process of treating rubber comprising adding thereto an organic accelerator and an amount of an aroma-producing alcohol'selected from the group consisting of phenyl ethyl alcohol, phenyl propyl alcohol, cinnamic alcohol, anisic alcohol, methyl phenyl carbinol, geraniol, citronellol, linalool, terpineol and borneol in an amount from 0.2% to 1.0% on the rubber, and vulcanizing the resulting mixture.

5. A cured rubber product of increased dura bility and pleasing odor containing cured in the rubber an organic accelerator and. not exceeding 1% on the rubber of a substance selected from the group consisting of aroma-producing alcohols and esters thereof.

6. A cured rubber product of increased durability and pleasing odor containing cured in the rubber an organic accelerator and not exceeding 1% on the rubber of phenyl ethyl alcohol.

ERIC C. KUNZ. FREDERICK J. MAYWALDL 

